This invention relates generally to portable respirator assemblies for supplying clean, breathable air to a worker's hood or face mask.
Generally speaking, such portable respirator assemblies have been known and used in the prior art. See, for example the portable back pack which contains a powered air purifying respirator as disclosed in J. R. Hilton U.S. Pat. No. 4,430,995 issued on Feb. 14, 1984. That assembly contains a pair of air filters connected to the inlet ports of an electric motor driven blower. The blower supplies filtered air from ambient surroundings to a collapsible/expandable bag which, in turn, supplies such air through a one-way valve and flexible air line to a worker's face mask. One end of the air bag is mounted against a back frame support and the other end of the bag, which expands and contracts, operates a spring biased arm to change the setting of a potentiometer which, in turn, changes the voltage applied by a battery to the blower motor so as to decrease the blower speed as the bag inflates and expands, and to increase the blower speed as the bag deflates and contracts. To prevent overinflation of the bag, the arm contacts a mechanical stop at the outer limit of bag expansion which throws a microswitch to cut off the power supply to the motor and stop the blower . One problem encountered with the subject assembly is its large size requiring that it be carried in a back frame attached to the back of the user. Another problem with this assembly is the fact that the blower speed continually changes during inhalation of the user, at least up to the point of blower cutoff at full bag expansion. Yet another problem of the subject assembly is that the blower speed is not subject to manual control by the user independent of his or her inhalation.
Another feature of certain prior art respirator systems is that of an audible low pressure alarm for warning the wearer of low air pressure in or supplied to a face mask or hood. See, for example, M. L. Kranz U.S. Pat. No. 4,250,876 issued on Feb. 17, 1981, M.L. Kranz et al. U.S. Pat. No. 4,498,471 issued on Feb. 12, 1985, T. A. Niemeyer U.S. Pat. No. 4,674,492 issued on June 23, 1987 and N. Fenger et al. U.S. Pat. No. 3,224,409 issued on Dec. 21, 1965. All of these low pressure alarms, however, are air operated whistles which must be used in conjunction with a source of compressed air which lend themselves to use with supplied air respirator systems. The reference alarm devices are not shown or described as being applicable to respirator systems operated in a powered air purifying respirator mode absent the use of an alarm operating compressed air source.
The respirator system of my invention overcomes these and other difficulties encountered in the prior art and provides an extremely compact assembly capable of being carried on the back of the user's waist belt.